a. Field of the Invention:
The present invention relates to a variant type of Gauss photographic lens which has a relative aperture of 1 : 1.4 and a field angle of about 45.degree. and which is intended for use with 35 mm single-lens reflex photographic cameras.
B. Description of the Prior Art:
In Gauss lens, the concave surface located immediately after the stop functions to produce spherical aberration, which has conventionally posed a problem to favourably correct the coma caused due to over-correction of said spherical aberration on the concave surface for rays at intermediate field angles. With a view to solving this problem, there have heretofore been designed numerous variants of Gauss lens and, of such variants, Simlar, which is an intermediate type between Sonner and Summar, is known most to those skilled in the art. As is already well known to the public, this type of lens has subsequently been developed into ones having larger relative apertures by replacing the intermediate lens element of the second cemented-truplet component with an air lens (space located between two lenses and functioning as a lens) and by splitting the lens located nearest the image side into two lens elements.
However, such variants and improved types of Gauss lens still have the above-mentioned defact of Gauss lens. In such types of lenses, spherical aberration is minimized by designing the three convex lens elements on the image side so as to meet the condition: EQU f.sub.5 &lt; f.sub.6 &lt; f.sub.7
wherein f.sub.5, f.sub.6 and f.sub.7 denote focal lengths of the convex lens elements respectively. However, this condition is never advantageous to eliminate flare though it is effective for minimizing spherical aberration.